Field of the Invention
The present invention relates to a display image generating device having a converting function of image resolution.
Description of the Related Art
In recent years, magnifying projection of images of documents (characters and charts, etc.) created by a personal computer (hereinafter referred to as PC) to a screen, using a projector, is carried out during a presentation, or a meeting, etc. The projector comprises a structure of converting an image signal input from the PC, etc., as an image signal, to a projection light by an image converting element such as a liquid crystal panel or micro mirror array, etc. There are projectors that comprise magnification display functions (hereinafter referred to as digital zoom function) that magnify and project images sent from the PC, etc., by carrying out data processing.
As a device for projecting for example, document references (newspapers, articles in magazines, or hand-written manuscripts), etc., or a three dimensional reference or object, a document camera is used. The document camera has a structure of transferring the image data generally photographed (imaged) by a CCD or MOS type imaging element to the projector via the PC, or directly to the projector.
In a case where the above described document camera is used, when an arbitrary region is requested to be projected by magnifying the region, a method of nearing the document camera to the document reference, etc., raising a zoom ratio if the document camera has an optical zoom, or a method of utilizing the above described magnification display function of the projector, is used. In that case of nearing the document camera to the document reference, an operation of matching the imaging region of the document camera with the to-be-displayed part of the document reference, etc. is carried out. This operation is burden for the user. Therefore, in most cases where a projector having a digital zoom function is used, the method using that function is adopted.
However, in a case where the digital zoom function that the projector has is used, there are problems such as below. The resolution of the image that the projector can project, differs according to the model, but is generally SVGA (800×600 pixels) to SXGA (1,024×1,024 pixels), and for example, in a case where an image data is sent from a PC to a projector, a processing of matching the resolution of the image to the resolution of the image that the projector can project, is carried out in advance.
Therefore, in a case where an arbitrary region of an image is projected magnified by the above described digital zoom function, the resolution of the magnified image reduces being proportional to the magnifying ratio. For example, in a case where the projector projects an image of SVGA and a magnification ratio of 1.25 times at SVGA, an image data of 800×600 pixels is generated by carrying out pixel interpolation on an image of 640×480 pixels. Especially in a case where an arbitrary region of an image of document reference, etc, imaged by a document camera is magnified, because the image is a natural image, the image quality after magnification drops remarkably.